Dear Phil,
It is good to see your contribution. I always enjoy your insight.
You mention that since the 1970s all work on theoretical physics including supersymmetry and string theory has failed to make contact with experiment. I think that you attribute this to a dearth of new experimental results at the energy frontier. An alternative possibility is a theory that predicts what we see and nothing else.
As I understand it, you believe the appropriate starting point for a theory of theories is modeled as a formal sum of the collection of mathematical universes; that is, every mathematical possibility has a corresponding physical possibility (more or less). I think you have explored this approach quite well.
An alternative approach would begin with one physical field, and nothing else, and attempt to derive our current universe from this field. That happens to be my preferred approach. I believe it is compatible with your answer that "up to energies tested so far there was simply "nothing new". I recall particle physicists a decade ago being sort of upset by the suggestion that the only particles that exist are those we know and resonances composed of those that we know. In fact I suggested that the Higgs was not a fundamental particle but just such a resonance. After several years of celebrating the Higgs, the latest Phys Rev Letters papers that I have seen are those analyzing Higgs as 'composite particle'.
You state: "in my opinion they are failing because they still cannot relinquish certain cherished philosophical beliefs." I fully agree with you. Now we just have to agree on the cherished beliefs in question!
My own belief is that the answer is more likely to come from the extreme that you explore, or the opposite extreme that I explore, than it is to come from anywhere in the middle.
My best regards, and good luck.
Edwin Eugene Klingman